[Haskell-cafe] Comment Syntax

[Albert Y. C. Lai]

I propose that only {- -} is comment; that is, -- is an operator token 
and not a marker of comments.

Two birds in one stone:

1. Removes the cause of the mistake of writing a haddock comment as --|
That is, if no one writes any comment with -- then no one writes any 
haddock comment with --| --^ etc.

2. Opens up the option of using -- for prefix unary negation, so that - 
is unambiguously infix subtraction and therefore (- x) is consistently 
right sectioning of infix subtraction.